1. Field of the Invention
The present invention relates to an image processing apparatus and method used in resizing of image data.
2. Description of the Related Art
Most of image sensors include a large number of effective pixels and a large number of ineffective pixels, which are arranged to surround the large number of effective pixels. A signal value of an effective pixel is used as image data, and that of an ineffective pixel is used to acquire correction data required to correct image data obtained from the effective pixel.
In order to resize image data obtained from such an image sensor, it is a common practice to use FIR digital filtering. Upon application of the FIR digital filtering, image processing is executed by making a convolution using a signal value of a pixel of interest, and signal values of a predetermined number of pixels around the pixel of interest. When the pixel of interest is located at an end portion of effective pixel, a filtering reference range includes ineffective pixels. For this reason, upon application of filtering for reduction processing, an additional effective pixel as a copy of an effective pixel located at the end portion is added to the outside of that effective pixel, and filtering is then applied.
Japanese Patent Laid-Open No. 11-154227 (to be referred to as literature 1 hereinafter) described an arrangement which outputs an image pyramid by generating a plurality of reduced images. In literature 1, a plurality of hierarchies of reduced images are generated by repeating a reduction process for executing additional effective pixel generation processing for adding an additional effective pixel to a border between an ineffective pixel and an effective pixel, and for applying filtering and down-sampling to an image having additional effective pixels. Such processing requires processing for judging a border between an effective pixel and an ineffective pixel in image data of each hierarchy, and adding an additional effective pixel to the border.
In general, in image processing for resizing image data, whether or not a filter reference range includes a border between an effective pixel and an ineffective pixel is judged, and if the border is included, an additional effective pixel is required to be added to outside of an effective pixel at an end portion. When the additional effective pixel generation processing is executed using image data during a video effective period in the reduction process of each hierarchy, a performance drop occurs in, for example, on-the-fly processing of movie shooting executed without the intervention of a DRAM.